Moveable walls economically provide flexibility to accommodate rapidly changing business environments by enabling the owners of space to rapidly reconfigure the space to accommodate changes in the business being conducted therein. Moveable walls find use in diverse market segments including health care delivery, education and retail space. In all of these segments, acoustical privacy is a concern. For example, in the delivery of health care a reasonable degree of confidentiality is expected. In a business environment acoustical privacy is necessary both to assure confidentiality and to provide a working environment relatively free from distraction.
Associated with the need to provide acoustical privacy and flexibility is the requirement to do so at a reasonable cost. Furthermore any structure must be made from materials which satisfy any regulatory authorities having jurisdiction over the space including electrical, building and fire inspection officials.
The satisfaction of regulatory authorities makes it desirable to incorporate construction materials which are in common use and with which the officials are therefore familiar. Accordingly, while it may be desirable from a cost perspective to use certain readily available and inexpensive sheet materials for constructing relocatable wall panels, such materials may prove undesirable if the relevant authorities having jurisdiction are unfamiliar with them and thus find them difficult to evaluate and accept for use.
As gypsum wallboard (also known as plasterboard, drywall and gypboard) is well accepted for fixed wall construction it is also highly desirable as a face material for relocatable wall construction. Gypsum wallboard is also desirable because of its being familiar to the construction trades which are quite familiar with its application and repair. Other materials which although suitable for wall construction, such as steel, are less desirable as they are associated with specialized industries not typically associated with construction. Also, the materials used to repair gypsum wallboard are readily available and non-toxic. The materials used to repair or work with other skin materials may be much more difficult to work with and may be deemed toxic or at least objectionable to the occupants of the space.
Gypsum wallboard is desirable for the manufacture of unitized (ie; moveable or relocatable) wall panels due to its ready availability, easy workability and low cost. Steel and other materials, while also candidates, tend to be expensive, more difficult to obtain if manufacturing is situated far from the source, and higher in cost.
Most sheet materials, and gypsum wallboard is no exception, experience an acoustical phenomenon referred to as a "coincidence dip". The coincidence dip occurs at a critical frequency at which the wavelength of free bending waves in a panel of sheet material coincides with the wavelength of sound in air. The coincidence dip is a reduction in average Transmission Loss (ie; more sound is transmitted) at frequencies just below the critical frequency to an octave or more above. The critical frequency depends on a material's stiffness and thickness. The frequency diminishes with an increase in stiffness or thickness.
Unfortunately the coincidence dip of most common wall construction materials, including gypsum wallboard occurs in the middle of the frequency spectrum of most importance to providing speech privacy. For 1/2 inch (approximately 12.7 mm) gypsum wallboard, the coincidence dip is centered around 3150 Hz.
The human ear does not hear all sounds equally. It is less sensitive to low frequencies and increasingly sensitive as frequencies rise. This contributes significantly to intelligibility. Vowel sounds, which carry relatively less meaning, are generally sounded at frequencies up to 1000 Hz.
Consonants in contrast are generally sounded at significantly higher frequencies, from 1500 Hz and up. Consonants contribute more to the intelligibility of speech than vowels. Consonants for example permit discernment between such words as "cat", "bat" and "hat". Removal of consonant sounds from speech is one manner to render speech unintelligible. Accordingly, a partition system in which higher frequency speech sounds are not well transmitted contributes greatly to privacy.
It is an object of the present invention to provide a sound attenuating relocatable partition wall panel having less of a coincidence dip than conventional panels.
It is a further object of the present invention to provide such a panel which is economical and which may incorporate common wall construction materials such as gypsum wallboard.